Noise reduction devices such as mufflers are well known. The following patents are exemplary of existing technology for the reduction of sound emitted by portable and large scale devices.
U.S. Pat. No. 5,214,254 to Russell T. Sheehan discloses a triple cone exhaust wave tuner which alters the resonant frequency of waves generated in the baffle chambers. However, it does not provide for attenuation.
U.S. Pat. No. 5,611,409 to Michael Arseneau discloses an exhaust muffler for small internal combustion engines. However, it is not applicable to large-scale machines with combustion engines.
U.S. Pat. No. 5,739,485 to Vincent Cholet et. al. discloses a three casing muffler for motor vehicles which attenuates high frequency exhaust noise. However, the muffler does not attenuate lower frequency sounds, which are more likely to be bothersome over a greater distance.
U.S. Pat. No. 4,046,219 to Nisar Shaikh discloses a muffler which attenuates high frequency exhaust noise from internal combustion engines, but does not account for low frequency noise.
Other methods of noise reduction include noise cancellation (i.e. the use of destructive interference to "cancel" a mechanical noise with artificially produced noise), the use of padding and insulation (using rubber, cellulose, and fiberglass), and the use of baffle plates for cars, airplanes, vacuum cleaners, lawn mowers, leaf blowers, snowblowers, and other portable devices.
The need exists for a muffler that more efficiently reduces the risk of hearing impairment and general discomfort. It is thus an object of the present invention to provide increased attenuation of engine noise through the use of a vacuum for sound encasement. It is another object to provide the chambers in a parabolic shape such that the reflection path is increased. It is still another object of the invention to provide a muffler which may be employed by different sized engines and motors.
These and other objects of the invention will become apparent to those skilled in the art from the following description.